1. Field of the Invention
This invention relates to a chain puller that is useful in salvage operations for hoisting or parbuckling marine objects such as ships or equipment, and specifically to an improved chain puller that includes a pair of chain stops that include gravity actuated chain securing doors.
2. Description of the Prior Art
The use of chain pullers, especially in salvage operations, is well known in the prior art. Typically, a chain puller is used to assist in hoisting and parbuckling operations in a marine environment for hauling up sunken ships and other submerged marine equipment. A chain puller is used with extremely strong chains with large links that may include a three inch diameter (the length of the chain link is approximately eighteen inches) and operate with maximum pulling forces that can be measured in hundreds of tons.
The pulling force is provided by hydraulically controlled moveable pistons driven by hydraulic fluid. Diesel engines connected to pumps are used for pumping the hydraulic fluid to the cylinders. The hydraulic pistons are connected at one end to movable rods that are in turn connected to pad eyes attached to a moveable chain stopper. During pulling, the chain is firmly engaged to the chain stopper that can only move a short distance (the length of the hydraulic cylinder piston rod) during each pulling sequence. The chain must be held in a static position by a second chain stopper when the hydraulic piston rod is returned to the start pull position.
One of the critical limitations of a chain puller is the ability to provide a large pulling force on the chain while at the same time being able to secure the chain in a fixed position when the hydraulic pistons and rods are being moved into place for the next pulling sequence. It is critical that the chain move in only one direction which is in the direction of the pulling force. It is important that the pulling chain be able to be stopped completely by the chain puller in a static position during periods of the operation in order to reposition the hydraulic actuators that move the chain.
The chain puller described herein includes two linearly aligned chain stoppers, each having a pair of doors that engage and release the chain that are not complex in operation, are activated by gravity and are extremely strong in fixing a chain so that the chain is movable only in one direction in use with the chain puller.